The process of forming or fabricating of a part or a structure often becomes the most critical factor in production, particularly when fatigue loading is present. When the welding is used as a fabrication process, the welded elements become the "weakest" regions of the structural element and, as a result, extra material is usually added to these regions on design stage, to prevent premature failure. For example, even in the case of butt welded joint ground flush to plate, the design stress range is still lower by 22-38% than the same parameter for the base material.

A number of engineering tools were developed to resolve the above-mentioned problem. For example, the application of Ultrasonic Peening (UP) may increase ("restore") the design stress range of welded elements, in some cases up to the fatigue strength of the base material. A software was developed for analysis of the influence of residual stresses on the fatigue life of welded elements and for Optimum Application of UP process. The developed Engineering Tools could be effectively applied on the stages of design, manufacturing and repair of parts and welded elements

The RESIsT is an Expert System for optimization of welded elements and structures by fatigue criterion. The following important parameters of welded structures with the goal to enhance the fatigue performance are analyzed:

The Ultrasonic Peening (UP) produces a number of beneficial effects in metals and alloys. Foremost among these is increasing the resistance of materials to surface-related failures, such as fatigue, fretting fatigue and stress corrosion cracking. The results of experimental studies showed that UP is the most efficient technique as compared with existing improvement treatments such as TIG-dressing, shot peening, hammer peening etc.